Comment on “A global environmental crisis 42,000 years ago”

John Hawks

doi:10.1126/science.abh1878

Abstract

Cooper et al . (Research Articles, 19 February 2021, p. 811) propose that a weakening geomagnetic field prior to the Laschamps Excursion explains megafaunal extinctions and human cultural changes that they claim happened 42,000 years ago. However, these authors misrepresent both the data and interpretations of cited work on extinctions and human cultural changes, so the specific claims they make about extinctions and cultural changes are false.

Highlights

Cooper et al (1) claim that a weaker geomagnetic field starting at 42 thousand years ago triggered a “global environmental crisis.” To support this idea, they examine Australian and Eurasian megafauna, Neanderthals, and human cultural transitions, claiming that many happened at or immediately after 42 ka
They examine Australian and Eurasian megafauna, Neanderthals, and human cultural transitions, claiming that many happened at or immediately after 42 ka. What they describe as a repeated occurrence of the number “42” for ancient extinctions prompted them to name the geomagnetic transition after the author Douglas Adams (1)
The conclusion of (3) is that the climate during the broad time interval represented by megafaunal extinctions is not different from earlier or later intervals, its title: “Climate change not to blame for late Quaternary megafauna extinctions in Australia.”

Summary

Introduction

Cooper et al (1) claim that a weaker geomagnetic field starting at 42 thousand years ago (ka) triggered a “global environmental crisis.” To support this idea, they examine Australian and Eurasian megafauna, Neanderthals, and human cultural transitions, claiming that many happened at or immediately after 42 ka. The cited work (2) states that “the timing of bottleneck and recovery in Tasmania are estimated to be 20,400 (6,440-36,520 95% CI) and 3,160 (192.8-16,960 95% CI) year BP respectively.” Cooper et al claim that Australian megafaunal extinctions happened around 42 ka, citing two sources.

Results

Conclusion